V6 Vortec to V8 Vortec Conversion

[JANETSKY, ALBERT (AIT)]

Hello All...

My name is Al Janetsky.  I'm a Systems Engineer with a telecommunications
organization... and for fun I'm converting a 1996 GMC Sonoma sportside
equiped with the 4.3L Central Sequential Fuel Injected Vortec to a 5.7L V8
Vortec. I'm hoping to keep the truck streetable with occasional runs on
Saturday nights at the local drag strip (for fun). 

The donor motor, wiring harness, and PCM is out of a 1998 3/4 ton GMC
Sierra.

I currently have the engine at Kendricks of San Antonio for my machine work.

Modifications include porting and resurfacing the Vortech heads.  An LT4 Hot
cam package... 1.6 roller rockers, and upgraded valve springs.  The specs on
the cam are 218/228 at .525/.525

I plan to swap out the v6 pcm for the v8 pcm... (even though they are
identical except for the programming).  I plan to use the existing v6 wiring
harness and run a few of the pinouts from the pcm to the fuel injector
assembly. I've already traced the pinouts from the ecm to the injectors, and
think that it will be a fairly straight forward swap.

There are a couple of major concerns that I have regarding my project.
First off -  Does anyone think this cam is too large for my conversion.  The
vehicle should weigh in at about 3275 after the v8 is installed.  Gearing on
the vehicle is a 3.08 locker, and the transmission is a 5 sp New Venture
3500 that I just rebuilt.  I know that I can give up some low end torque...
and it looks like this cam will make gobs (in comparison to existing) of
power way up in the rpm range.

A computer program at the machine shop speced out about 330HP with the use
of small tube headers and somewhere near the 400 ft/lbs of torque mark.  I'm
concerned that the PCM will not be able to handle all of the duration.

Some other areas that I would like to address are the identification of the
98 OBD-II PCM and how I might be able to custom program the system to be
more compatible with the modifications... (including tach, gearing, manaul
trans, etc. etc.)

I'm willing to spend time doing the research... but so far it appears that
most of the information on the web is related to older efi systems.  I've
considered the hypertech solution... but to me, it's only a duct tape
solution being that I can't fine tune the system to my needs.

I'd really appreciate any information about the 98 pcm, communication
protocols, etc that would get me started in the proper direction.

Thankyou,

Albert Janetsky
aj5242 at txmail.sbc.com
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org